Re: explicit dcache <-> user-space cache coherency, sys_mark_dir_clean(), O_CLEAN

Pavel Machek
2004-02-23T13:24:55Z

Hi!

> generation counters are problematic if they are not persistent. But
> there's a pretty natural persistent 'generation counter' which could be
> used for Samba's purpose: the mtime of the directory. The problem right
> now is that it doesnt have enough resolution to be a true unique
> generation counter. But having high-resolution mtime is a goal anyway.
>
> XFS is one filesystem that has high-resolution mtime:
>
> typedef struct xfs_timestamp {
> __int32_t t_sec; /* timestamp seconds */
> __int32_t t_nsec; /* timestamp nanoseconds */
> } xfs_timestamp_t;
>
> monotonity is important: two successive directory operations to not be
> possible within the same nanosecond. This is not possible with current
> hardware - but how about future hardware? Can we make an assumption like
> this?

Does not ndelay(1) if samba notices mtime is too young in the samba code
fix that?
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64 bytes from 195.113.31.123: icmp_seq=28 ttl=51 time=448769.1 ms